The present invention relates to the printing and/or copying arts. It finds particular application in conjunction with sheet feeders for printers, copiers, etc., and will be described with particular reference thereto. However, it is to be appreciated that the present invention is also amenable to other like applications, marking devices, and/or print engines, e.g., facsimile machines, multi-function peripherals/printers (MFPs), etc.
In the case of copiers, printers and the like (hereinafter all referred to generally as print engines), often a sheet feeder is employed to supply sheets of paper, transparencies, or other like media to a marking device or engine where toner, ink or the like is applied thereto in accordance with an input image or data. Typically, it is desired to select one sheet at a time from a stack of sheets in a paper tray of the sheet feeder. Nevertheless, a problem exists, known as multi-pick, whereby a plurality (e.g., two or three or sometimes even more) sheets are picked from the sheet feeder""s paper tray at one time. Multi-picks tend to be most prevalent when the stack of sheets is low or the paper tray is near empty. Multi-picks result when the attractive force (e.g., caused by compression together, friction, static, etc.) between a top sheet in the stack and an underlying sheet or sheets is not overcome as the top sheet is advanced from the sheet feeder. If the force is not overcome, the underlying sheet or sheets is/are advanced from the sheet feeder along with the top sheet, hence, a multi-pick results.
In general, it is known in the art to use pick-roller systems to select or pick sheets from the paper tray of the sheet feeder. However, due to the design and/or operation of previously developed pick-roller systems, they still undesirably experience multi-picks at times. Accordingly, it is remains desirable to have a pick-roller assembly and/or method which suitably inhibits multi-picks.
The present invention contemplates a new and improved pick-roller driver and/or pick-roller method which overcomes the above-referenced problems and others.
In accordance with an aspect of the present invention, a sheet feeder is provided for a print engine. The sheet feeder includes a paper tray which holds a stack of sheets including a top sheet, and a pick-roller which makes contact with the top sheet. The pick-roller is rotatable about an axis. Also included is a driver, which upon forward energizing, rotationally drives the pick-roller about the axis in a forward direction to advance the top sheet to sheet advancing means that pass the top sheet along through the print engine. A drive controller controls the driver. The drive controller causes the pick-roller to be released for free-wheeling after advancing the top sheet to the sheet advancing means.
In accordance with another aspect of the present invention, a method is provided for feeding sheets out of a sheet feeder to a print engine. The method includes: holding a plurality of sheets; contacting one of the plurality of sheets with a rotary member; selectively rotating the rotary member in a first direction such that the sheet in contact therewith advances to sheet advancing means that pass it along through the print engine; and, releasing the rotary member for free-wheeling upon the advanced sheet reaching the sheet advancing means.
In accordance with yet another aspect of the present invention, a sheet feeding device includes: holding means for holding a plurality of sheets; sheet advancing means for passing sheets from the sheet feeding device along through an associated print engine; rotary means for advancing one of the plurality of sheets from the holding means to the sheet advancing means; drive means for rotating the rotary means in a first direction thereby advancing the sheet from the holding means to the sheet advancing means; and, control means for controlling the drive means. The control means causes the rotary means to be released for free-wheeling when the sheet advanced by the rotary means reaches the sheet advancing means.
In accordance with still another aspect of the present invention, a print engine includes a marking engine which applies marks to sheets of media supplied thereto and a feeding device which supplies the sheets to the marking engine. The sheet feeding device includes: a paper tray which holds a plurality of sheets; a pick-roller which makes contact with one of the plurality of sheets; a driver, which upon forward energizing, rotationally drives the pick-roller to advance the sheet in contact therewith to sheet advancing means that pass it from the feeding device to the marking engine; and, a drive controller which controls the driver. The drive controller causes the pick-roller to be released for free-wheeling after advancing the sheet to the sheet advancing means.
One advantage of the present invention is that it provides suitable sheet feeding for print engines while guarding against multi-picks.
Still further advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.